President Bush's chief domestic security official yesterday apologised for the disruption of a big MI5 and police surveillance operation in Britain.

Tom Ridge, the homeland security secretary, said the leaking of intelligence in the US about alleged terrorist suspects here was "regrettable".

Mr Ridge was speaking to journalists in London before meeting David Blunkett and Sir David Omand, the prime minister's security and intelligence coordinator.

Whitehall was furious early last month when individuals were named and allegations about terrorist attacks were made public in the US.

The claims, about putative attacks on buildings in the US and on British targets, including Heathrow, were based on information found on the computers of an alleged al-Qaida sympathiser in Pakistan.

The disclosures forced the police to quickly arrest 12 suspects in raids across England.

In Blackburn, Lancashire, armed officers pulled two men out of a Mercedes, and in Luton, Bedfordshire, neighbours told how dozens of police had halted a red Nissan in a residential street and pinned the driver against the door for almost three hours.

Anti-terrorist officials here have been seriously concerned about the disclosure of infor mation in America which, they say, could prejudice the outcome of prosecutions.

They are also unhappy about the frequency of public warnings in the US about possible attacks - something which, say Whitehall officials, could lead to the dangers of "crying wolf" or "threat fatigue".

Mr Ridge said that the US had raised its threat level and placed extra armed guards around buildings because of "credible" and "specific" information coming from Pakistan.

"The volume of potential information was the largest we have ever seen," he said.

He added that there was credible intelligence of terrorist plans to "disrupt the democratic process" in the US.

The "intent" had been exposed but there was no specific intelligence, he said.

Asked about the impact of a terrorist attack in the run-up to November's presidential election, Mr Ridge said it would unify the US "more than ever".

A joint contact group has been set up in which the US and Britain share counter-terrorist information.

One proposal being discussed is an international register whereby frequent travellers would voluntarily provide information to security agencies and airlines about their personal characteristics so that they can pass security controls more quickly.